International journal of mass spectrometry and ion physics

The construction and performance of a two-stage electron energy selector of the double-hemispherical type are described. Energy half-widths of 0.06–0.12 V in the electron beam have been obtained with operating voltages of 10–30 V in the hemispherical stages. No magnetic shielding was employed. Resolved electron currents of 2 × 10−8 A at a half-width of 0.07 V were obtained, in the form of a well-collimated beam which was passed axially through a cylindrical reaction chamber. Preliminary results without mass resolution on metastable-atom and positive-ion formation are reported, together with later results on formation of Ar+ and Kr+ using a quadrupole mass filter, in rare gases.

A two-stage double-hemispherical electron energy selector